This invention relates generally to fluid pressure motors. More specifically, this invention relates to fluid pressure motors of the springdiaphragm type which may also be of the "rolling" or convoluted diaphragm configuration. With still greater particularity, this invention relates to a particular diaphragm structure and method of making such a diaphragm for the above-described types of fluid pressure motors.
Conventional diaphragms for "rolling" diaphragm fluid pressure motors are constructed by forming an essentially hat shaped fabric part which is thereafter impregnated with an elastomer to render the diaphragm gas impermeable. Generally the fabric from which the hat shaped part is formed is a square weave of fibrous material, either stranded or twisted together. When such a square weave fabric is formed into a hat shaped configuration, the walls of the cylindrical portion of the hat, which later become the "rolling" or convoluted part of the diaphragm, have four areas within which the fibers of the square weave extend radially and transversely. These radially extending fibers are able to flex easily as the diaphragm "rolls" during action of the fluid pressure motor, and the transverse fibers are carried along without significant relative movement between the radial and transverse fibers. However, the square weave of the fabric also results in there being four areas of the cylindrical portion of the diaphragm wherein the fibers of the weave lie at substantially 45 degrees to a radial line. When the fibers within these latter portions of the diaphragm "roll" through the convoluted part of the diaphragm as the actuator moves, the fibers move angularly relative to one another in somewhat of a sawing or teeter-totter motion. The Applicants have discovered that conventional elastomerically impregnated fabric rolling diaphragms, because of this aforementioned sawing of the fibers in certain areas of the diaphragm, experience an overstressing of the elastomer in these areas and eventual failure of the diaphragm.
A conventional teaching which seeks to improve the flexibility of the diaphragm is illustrated by U.S. Pat. No. 2,730,131 issued to H. L. Asp et al wherein a somewhat flat diaphragm intended for relatively short movement is formed by cutting a disk from a thick walled cylinder of material such as Teflon. Prior to severing the disk from the cylinder, a multitude of axially transverse radial cuts are made extending from the outer perimeter of the incomplete disk, which is to become the diaphragm, part way to the center thereof. This multitude of radially extending cuts results in a completed diaphragm having a plurality of distinct transverse layers which are separately movable relative to one another during flexing of the diaphragm. However, the diaphragm taught by the Asp et al patent is not taught as being appropriate for use in a rolling diaphragm type of fluid pressure motor. Further, the Asp et al diaphragm does not incorporate any type of fabric or fibrous reinforcement within the impermeable flexible or elastomeric material from which the diaphragm is formed. This lack of fabric reinforcement within the diaphragm as taught by Asp et al is believed by the Applicants to result in a diaphragm having relatively limited pressure capabilities. It is clear that the diaphragm as taught by Asp et al must rely entirely upon the strength of the elastomer alone to resist the forces imposed upon the diaphragm by operating pressure of the fluid motor.
A fabric reinforced elastomeric membrane is taught by U.S. Pat. No. 3,376,898 issued to Hugley, wherein the membrane is subdivided into discrete axially extending layers to enhance the flexibility of the membrane. However, the cylindrical membrane teaching of the Hugley patent is not seen by the Applicants as being applicable to the making of diaphragms for rolling diaphragm type of fluid motors. While the Hugley patent does teach a fluid impermeable membrane having a plurality of distinct layers which are relatively movable, it is noted that each one of the layers within the membrane is composed of a fibrous fabric impregnated with an elastomer. In this respect then the Hugley patent will be seen to aggregate conventional diaphragm teachings.